💾 4040 #1 Part 1 - It was supposed to be so easy!

This week I tackle a new (to me) Commodore 4040 disk drive which won’t boot 💀. I hunt down the culprit preventing it from booting, and deep dive into a disassembly of the secondary processor’s startup ROM code. 🔍⚡

As well as tracking down the problem causing it to fail to boot, I run through a disassembly of the secondary processor’s ROM startup ROM.

📚 Building my library of IEEE-488 drive ROM disassemblies at: https://github.com/piersfinlayson/cbm-ieee-disk-diag-rom
Check the docs/original_roms folder - branch 0.2.2 has the latest disassemblies!

🛒 Get your 6504 and 6530 replacement boards:

6530 RRIOT: https://piers.rocks/u/dd6530
6504 CPU: https://piers.rocks/u/rb6504

⏰ Timestamps
00:00 🎬 Introduction
01:39 💥 Failure mode
03:28 📋 Secondary ROM disassembly
10:17 🔄 Replace 6504
10:38 🔧 Remove VIA/6522
11:01 ⚡ Replace RRIOT/6530
11:20 🎉 It boots …
13:37 💭 Final thoughts